The present invention relates in general to telephone call distribution systems and, in particular, to distribution systems for handling 911 type calls.
Traditional 911 call distribution arrangements servicing complex metropolitan areas utilize a centralized switch to route 9-1-1 calls to the correct PSAP (Public Safety Answering Point). Additional equipment is required at the PSAP to distribute calls to answering positions. On-premise equipment is an undue cost and maintenance burden, particularly for PSAPs with few answering positions. The present invention provides a solution to this drawback in the prior art with a switch that centralizes call distribution to individual answering positions as it routes the call to the correct PSAP.
Enhanced 911(E911), consists of three major features selective routing, Automatic Number Identification (ANI), and Automatic Location Identification (ALI). Selective routing, implemented through a control office, is the ability to route a call to the correct answering point, that is the one which serves the calling party's area. It is provided by using the calling party's telephone number forwarded to the control office by that party's end office using ANI forwarding trunks and protocols. The control office translates the number into a correct route choice. In E911 the term ANI describes the ability to display the calling party's telephone number at answering point positions by forwarding the number to the PSAP over ANI trunks, typically TSPS-type, and decoding it for display. The ANI is in turn used as a key to a record in an ALI data base. That record contains extended calling party information, including address, class of service, and serving emergency agencies. ANI and ALI are life-saving features when the calling party cannot provide location information for some reason. Enhanced 911 with selective routing is a necessity in metropolitan areas where a central city is ringed by a number of smaller communities which abut one another, but where each community wants to continue receiving and dispatching its own emergency calls.
In addition to these features, some large cities have benefited from a fourth set of features by implementing an on-premises automatic call distribution (ACD). very useful ACD features include queuing calls for order of arrival service, equitable distribution between attendants, and detailed traffic reports.
Previously, there has not been a cost-effective way of providing advanced call-handling features to small communities with, for example, four to ten emergency answering and overflow positions. The customer equipment to deliver those features is quite expensive at low position count. Four aspects which are lacking in prior art systems are cost effectiveness for small answering points, a full set of user points, a full set of user features including ACD capabilities, ease of use, and compatibility with current system elements.
The cost-effectiveness goal must address the small size of many agencies and their commensurate small budgets for equipment and ongoing expenses. It must also address the distance that small or large answering points might be from a control office. In response to the small size problem, a centralized system is needed where the application control is shared by many agencies. The distance issue implies that a pair of circuits, one data, one voice, for each position could offset centralized application control economics and thus needs to be avoided. This leads to a requirement for a single circuit supporting both voice and data requirements.
ACD features are important tools to agencies who have them. Traffic and call handling summary reports are especially useful for scheduling and, to a growing extent, crime analysis. Beyond centralization of fundamental E911 features, an application need is to provide queuing, call distribution and control, reports, and supervisory features in the package.
All communities handle emergency calls in some way today. Basic and enhanced 9-1-1 systems have been deployed. A new system must be compatible with as much of the existing system as possible. The obvious compatibility issues are with signaling protocols and interfaces to existing central office and customer-premises hardware. Another compatibility issue is with the current call handling procedures. In many cases, it is desirable to retain aspects of the previous system, for example, in the handling of administrative and alarm service calls. To maximize compatibility requires that the displacing system be very flexible.
The present invention fulfills these requirements and provides a system which overcomes the drawbacks in prior art systems.